STATE OF MONTANA

AIR QUALITY MONITORING NETWORK PLAN

June 2020

Montana Department of Environmental Quality Air Quality Bureau

1520 East 6th Ave

Helena, MT 59601

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Contents

Introduction ............................................................................................................................... 1

I. Ambient Air Monitoring Requirements ................................................................................... 2

A. Ozone (O3) Monitoring Criteria ................................................................................... 2

B. Carbon Monoxide (CO) Monitoring Criteria ................................................................ 4

C. Nitrogen Dioxide (NO2) Monitoring Criteria ............................................................... 4

D. Sulfur Dioxide (SO2) Monitoring Criteria ...................................................................... 5

E. Lead (Pb) Monitoring Criteria ....................................................................................... 7

F. Particulate Matter (PM10) Monitoring Criteria .............................................................. 8

G. Fine Particulate Matter (PM2.5) Monitoring Criteria ..................................................... 9

H. National Core Monitoring Site (NCore) Monitoring Criteria ....................................... 11

I. General Monitoring Network Design Considerations ................................................. 11

II. Changes to the Monitoring Network ................................................................................... 13

III. Appendices ....................................................................................................................... 14

Appendix A, Monitoring Site Locations ........................................................................... 15

Appendix B, Montana Core Based Statistical Areas ......................................................... 18

Appendix C, Monitoring Network Summary ................................................................... 21

Appendix D, 2019 Ambient Air Quality Raw Data Summary .......................................... 24

Appendix E, PM2.5 Speciation Analytes ............................................................................ 26

Appendix F, National and Montana Ambient Air Quality Standards ................................ 29

Appendix G, Annual SO2 DRR Report............................................................................ 31

Appendix H, Public Inspection & Comment ................................................................... 33

Appendix I, Public Comment Recieved ........................................................................... 35

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Introduction This Air Quality Monitoring Network Plan (Plan) is developed and submitted on an annual basis in accordance with the requirements contained in Title 40 of the Code of Federal Regulations (CFR) Part 58.10. The intent of this plan is to accurately describe the monitoring sites in the Montana Department of Environmental Quality’s (DEQ) network, identify each site’s monitoring purpose, describe how the sites fulfill Network Design Criteria (40 CFR 58, Appendix D), and describe any deviations in physical characteristics or operation from regulatory requirements. The Plan also describes changes the DEQ anticipates making to the network in the next year. In turn, providing opportunity for the DEQ to solicit, evaluate, and respond to comments and input from County Agencies, the general public, and other DEQ interests regarding the network. The Plan development process establishes the structure for DEQ to evaluate its existing ambient air monitoring network and to tailor the network based on modified data needs, changing regulatory requirements, and available resources. DEQ monitors air quality principally by measuring concentrations of criteria air pollutants pursuant to the federal Clean Air Act (CAA) in an endeavor to meet three basic monitoring objectives:

1. Provide air pollution data to the general public in a timely manner. 2. Support compliance with ambient air quality standards and emissions strategy development. 3. Support air pollution research studies.

Criteria air pollutants are the most common air pollutants with known harmful human health effects. The six criteria pollutants are:

▪ carbon monoxide (CO) ▪ sulfur dioxide (SO2) ▪ lead (Pb) ▪ nitrogen dioxide (NO2) ▪ ozone (O3) ▪ particulate matter (PM). PM includes airborne materials in two size fractions, those with an

aerodynamic diameter of 10 microns and less (PM10), and those with an aerodynamic diameter of 2.5 microns and less (PM2.5).

For each criteria air pollutant, National Ambient Air Quality Standards (NAAQS) are established to protect public health and the environment. Two types of federally-mandated air quality standards may exist. Primary standards set limits to protect public health, including the health of at-risk populations such as people with pre-existing heart or lung disease (e.g. asthmatics), children, and older adults. Secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings. Montana has adopted similar air quality standards known as the Montana Ambient Air Quality Standards (MAAQS). This Plan is presented in three broad sections. The first section describes the various pollutant-specific ambient air monitoring design requirements and explains how the DEQ has implemented each as applicable. The second section describes changes to the monitoring network that the DEQ is proposing. The final section includes appendices which provide supplemental information and data in support of specific elements outlined within this Plan.

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I. Ambient Air Monitoring Requirements The term ‘ambient air’ is defined in 40 CFR 50.1 as “that portion of the atmosphere, external to buildings, to which the general public has access.“ Federal rules implemented by the United States Environmental Protection Agency (EPA) require each state to establish a network of monitors to measure concentrations of criteria pollutants in ambient air based upon population, regional air quality, and regulatory concerns. The following sections summarize the ambient air monitoring requirements for each of the criteria air pollutants, and explain the DEQ’s implementation.

A. Ozone (O3) Monitoring Criteria The minimum number of ozone monitors required by 40 CFR Part 58, Appendix D is summarized in Table 1.

Table 1 - Minimum O3 Monitoring Requirements(1)

Metropolitan Statistical Area (MSA) population(2,3)

Number of Monitors per MSA

Most recent 3-year design value concentrations ≥ 85 percent (%) of

any O3 NAAQS(4)

Most recent 3-year design value concentrations < 85% of any O3

NAAQS(4,5)

>10 million 4 2

4 – 10 million 3 1

350,000 – <4 million 2 1

50,000 – <350,000(6) 1 0 (1) From Table D-2 of Appendix D to 40 CFR Part 58 (2) Minimum monitoring requirements apply to the metropolitan statistical area (MSA) (3) Population based on latest available census figures. (4) O3 NAAQS levels and forms are defined in 40 CFR Part 50. (5) These minimum monitoring requirements apply in the absence of a design value. (6) An MSA must contain an urbanized area of 50,000 or more population.

As described in Appendix B to this Plan, there are three Metropolitan Statistical Areas (MSAs) in Montana, and all three fall within the 50,000 to 350,000 population category. The three MSAs are Billings, Missoula, and Great Falls. At present, O3 monitoring is being conducted in Missoula as representative of these three areas. DEQ previously conducted O3 monitoring in the Billings area from 2005 to 2007 (station number 30-111-0086). In Great Falls, historical monitoring data, meteorological patterns, and professional judgment indicate that monitoring in this MSA is not warranted given the low O3 levels monitored in the two larger MSAs and the consistently windy conditions that exist in Great Falls. Beyond monitoring efforts related to the three MSAs, the DEQ has endeavored, in several cases with collaborative funding from the Bureau of Land Management (BLM), to define background levels of O3 across Montana and to assess impacts from petroleum exploration within the eastern portion of the state. DEQ conducts O3 monitoring in Broadus (30-075-0001), Birney (30-087-0001), Sidney (30-083-0002), Malta (30-071-0010), Lewistown (30-027-0006), and at the National Core Monitoring Site (NCore) (30-049-0004). See Appendix A of this Plan for a map displaying the location of these sites. Table 2 summarizes the 8-hour rolling average O3 values measured at monitoring sites operated by the DEQ during the designated 2019 ozone season (April – September), while Table 3 summarizes the 8-hour O3 values measured at monitoring sites operated by the DEQ during the entire calendar year.

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Table 2 – 8-Hour Rolling Monitored O3 Values for Ozone Season 2019(1)

Station

Concentrations (ppm) NAAQS Design Values (ppm)(2)

Minimum Maximum Average 2019 2017 – 2019

Birney 0.003 0.061 0.030 0.057 0.058

Broadus 0.007 0.064 0.033 0.064 0.063

Lewistown 0.007 0.059 0.034 0.058 0.060

Malta 0.006 0.061 0.032 0.056 0.056

Missoula -- -- -- -- 0.049

NCore 0.005 0.059 0.035 0.062 0.061

Sidney-201 0.01 0.068 0.033 0.057 0.058

(1) Ozone Monitoring Season established under 40 CFR Part 58, Table D-3

(2) Design Values calculated by the USEPA Air Quality System (AQS) database -- Insufficient data collected

Table 3 – 8-Hour Rolling Monitored O3 2019 Annual Values

Station

Concentrations (ppm)

Minimum Maximum Average

Birney 0.003 0.061 0.029

Broadus 0.007 0.064 0.033

Lewistown 0.007 0.064 0.035

Malta 0.006 0.061 0.030

Missoula -- -- --

NCore 0.005 0.066 0.034

Sidney-201 0.01 0.068 0.033

-- Insufficient data collected

As demonstrated in Tables 2 and 3, minor variability has been observed in the monitored ambient O3 concentrations across the state. The 8-hour O3 design value of 0.059 ppm collected in the Billings area during 2005-2007 further illustrates this occurrence. The dynamic becomes particularly interesting given the spatial breadth and population diversity of these sites. Two of the seven monitoring sites (including the 2005–2007 Billings site) are located in the two largest-population communities in Montana, two are in small towns, one is in a rural oilfield, two are in very rural settings with minimal population and no industry, and one is in a pristine background location adjacent to a federal wilderness area. It appears, that the O3 monitored in the ambient air across Montana is indicative of general background concentrations produced principally by natural sources or transported in from sources outside the state, with little anthropogenic source input from within Montana. The monitoring directives in 40 CFR Appendix D, Section 5 contain specific requirements for the operation of Photochemical Assessment Monitoring Stations (PAMS) in areas classified as serious, severe, or extreme nonattainment for O3. Montana does not contain any O3 nonattainment areas, therefore PAMS monitoring is not required of the DEQ.

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B. Carbon Monoxide (CO) Monitoring Criteria Per 40 CFR 58 Appendix D Section 4.2, the requirements for CO monitoring sites are closely related to the requirements for near-road NO2 monitoring sites (see Section I.C. of this Plan). Table 4 summarizes the number of required CO monitoring sites.

Table 4 – Minimum CO Monitoring Requirements(1)

Criteria(2) Number of Near-Road CO Monitors Required

CBSA Population ≥ 1,000,000 One, collocated with an NO2 monitor or in an alternative

location approved by the EPA Regional Administrator

(1) From Appendix D to 40 CFR Part 58, Sec 4.2.1 (2) CBSA populations based on latest available census figures

As documented in Appendix B to this Plan, no Montana Core Based Statistical Areas (CBSAs) meet the listed criteria, and no CO monitors are required in Montana on this basis. Historically, the DEQ and local county air programs have conducted CO monitoring in various larger communities in the state where motor vehicle emissions had caused ambient air concerns. However, because of the improvement of traffic patterns and the gradual renewal of the general vehicle fleet to newer, cleaner-burning engines, monitored CO concentrations in ambient air remain extremely low. As a result, DEQ discontinued its traffic-related CO monitoring with EPA approval, and no community CO monitoring is currently being conducted. The DEQ continues to operate one trace-level CO monitor at the NCore station north of Helena to track background concentrations of this pollutant over time. Section I.H describes NCore monitoring efforts. Table 5 summarizes the 1-hour CO values measured at the NCore monitoring site during 2019.

Table 5 – 1-Hour Monitored CO Values for 2019

Station

Concentrations (ppm)

Min Max Average

NCore 7 728 128

C. Nitrogen Dioxide (NO2) Monitoring Criteria The minimum number of NO2 monitoring sites required by 40 CFR 58 Appendix D Section 4.3 is summarized in Table 6.

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Table 6 – Minimum NO2 Monitoring Requirements(1)

Requirement Type Criteria(2) Minimum

NO2 Monitors Required

Near Road

CBSA Population ≥ 500,000 1

CBSA Population ≥ 2.5 million 2

CBSA Population ≥ 500,000 and Road Segments with annual average daily traffic counts ≥250,000

2

Area-Wide CBSA Population ≥ 1 million 1

Requirement Type Criteria(2) Minimum

NO2 Monitors Required

Protection of Susceptible and Vulnerable Populations

Any area inside or outside CBSAs As Required by EPA Regional Administrator and Appendix D

Section 4.3.4(b).

(1) From Appendix D to 40 CFR Part 58, Sec 4.3.1 (2) CBSA populations based on latest available census figures

As demonstrated in Appendix B, no Montana communities meet any of the criteria listed in Table 6, and no additional NO2 monitoring has been required of DEQ by the Regional EPA Administrator; therefore no ambient NO2 monitors are currently required in Montana. However, the DEQ currently operates five NO2 monitoring sites in an effort to determine NO2 background concentrations along with potential impacts associated with the oil and gas industry in the eastern part of the state. NO2 is monitored at Sidney (30-083-0002), Broadus (30-075-0001), and Birney (30-087-0001), as well as Malta (30-071-0010) and Lewistown (30-027-0006) which are operated in partnership with the BLM in an attempt to further define background concentrations and spatial distribution of this pollutant within the state of Montana. Table 7 summarizes the 1-hour NO2 values measured at monitoring sites operated by the DEQ during 2019.

Table 7 – 1-Hour Monitored NO2 Values for 2019

Site

Concentrations (ppb) NAAQS Design Values (ppb)(1)

Min Max Average 2019 2017 – 2019

Birney 0 11.0 0.66 6.0 9

Broadus 0 14.0 0.82 10.0 10

Lewistown 0 14.0 0.68 11.0 10

Malta 0 15.0 0.69 7.0 8

Sidney – 201 0 15.0 1.18 11.0 10 (1) Design Values calculated by the USEPA Air Quality System database

D. Sulfur Dioxide (SO2) Monitoring Criteria The minimum number of SO2 monitoring sites required by 40 CFR 58 Appendix D Section 4.4 is summarized within Table 8.

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Table 8 – Minimum SO2 Monitoring Requirements(1)

CBSA PWEI(2)(3) Minimum Number of SO2

Monitors Required

≥1,000,000 3

<1,000,000 - ≥100,000 2

<100,000 - ≥5,000 1

(1) From Appendix D to 40 CFR Part 58, Sec 4.4.2 (2) CBSA populations based on latest available census figures (3) Core Based Statistical Area Population Weighted Emissions Index

This EPA criteria used to determine the number of required SO2 monitors is based on two metrics: the CBSA—(a county or counties with at least one urbanized area of at least 10,000 people population), and the Population Weighted Emissions Index (PWEI -- the population in the CBSA multiplied by the annual tons of SO2 emitted using the most recent aggregated emissions data available in the National Emissions Inventory, divided by 1,000,000). The Billings CBSA is the only CBSA in Montana that has the potential to require SO2 monitoring based on these prescribed metrics. Table 9 summarizes the current PWEI for the Billings CBSA using the latest published National Emission Inventory (NEI) values.

Table 9 – Billings CBSA PWEI Calculation

Population(1) (a)

Reported Emission(2) (b)

PWEI(3) (c)

172,846 4710.1 814

(1) US Census Bureau Population Estimate as of July 1, 2019 (2) 2017 National Emissions Inventory (Yellowstone, Golden Valley and Carbon County) (3) PWEI (c) = a x b/1,000,000

SO2 monitoring is triggered within a CBSA when the calculated WPEI value is equal to or greater than 5,000. Based on the prescribed criteria, neither Billings nor any of the other Montana CBSAs present an SO2 PWEI that approaches or exceeds 5,000. Consequently, no DEQ SO2 monitoring is required based on the PWEI criteria. DEQ continues to operate one long-term SO2 monitor at the Coburn Road site in Billings (30-111-0066) as part of the approved Maintenance Plan (81 FR 28718, Resdesignation Request and Associated Maintenance Plan for Billings, MT 2010 SO2 Nonattainment Area) to provide an ongoing assessment of SO2 compliance in the Billings area. The Coburn Road site, located within the former Yellowstone County (partial) SO2 Nonattainment Area, has been in continuous operation since 1981 as a State or Local Air Monitoring Station (SLAMS) site for NAAQS comparison purposes. Additionally, DEQ operates one SO2 monitor at the Sidney site (30-083-0002) to assess impacts from oil and gas production in eastern Montana, and one trace-level background monitor at the NCore station (30-049-0004). Section I.H describes NCore monitoring. Table 10 summarizes the 1-hour values measured at the SO2 monitoring sites operated by the DEQ during 2019.

Table 10 – 1-Hour Monitored SO2 Values for 2019

Site

Concentrations (ppb) NAAQS Design Values (ppb)(1)

Min Max Average 2019 2017 - 2019

Billings - Coburn Road 0 26.5 4.27 18 24

NCore - Sieben's Flat 0 18.4 0.50 3 5

Sidney - 201 0 14.4 1.14 9 17

(1) Design Values calculated by the USEPA Air Quality System database

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Beyond DEQ-operated monitors, ambient SO2 is monitored by industrial sources in the communities of Great Falls and Billings. In the Great Falls area, one SO2 monitoring location (Race Track Site, 30-013-2001) in the community of Black Eagle is operated by the Calumet Montana Refining Company, LLC (Calumet) as required by their air quality permit. Data from this site is not entered into the AQS database but is used by DEQ’s air quality compliance program. In the Billings/Laurel area there is currently a single industry-operated SO2 monitoring site (Johnson Lane, 30-111-2006), maintained by Yellowstone Electric Limited Partnership (YELP) as a condition of their air quality permit. Three additional monitors were historically operated by a consortium of local SO2-emitting industries, known as the Billings Laurel Air Quality Technical Committee (BLAQTC). The Brickyard (30-111-2005) and Laurel (30-111-0016) sites were discontinued in June of 2015; while the third site, Lockwood (30-111-1065), failed in 2011 and was not replaced. The DEQ performed periodic quality assurance audits of these sites and has entered their data into AQS, but suspended these efforts in 2011 due to resource constraints. Both YELP and BLAQTC performed monitoring under an approved Quality Assurance Project Plan (QAPP) as individual Primary Quality Assurance Organizations (PQAOs) independent of the DEQ. DEQ believes that the data obtained from the YELP and BLAQTC monitors met the commitments of the individual QAPPs and are therefore of regulatory quality. DEQ looks principally to the Coburn Road SLAMS monitor for NAAQS compliance determination in the Billings area, but has historically examined, and continues to examine, available data for contrast and comparison purposes. On August 10, 2015, EPA finalized the Data Requirements Rule (DRR) for the 2010 1-hour SO2 primary NAAQS (40 CFR 51, Subpart BB). The SO2 DRR required that air agencies identify and characterize air quality around large sources. Talen Montana, LLC’s (Talen) Colstrip Steam Electric Station located in Rosebud County was the sole source in Montana identified as applicable to the rule. As required in the rule for characterizing air quality for the primary 2010 SO2 NAAQS, Montana submitted the appropriate designation of attainment for Rosebud County as demonstrated through modeling on December 20, 2016. On January 9, 2018 within 83 Federal Register (FR) 1098, EPA published a notice that they agreed with Montana’s determination and designated Rosebud county as Attaining/Unclassifiable for the 2010 SO2 standard. In the same notice EPA designated all the remaining counties in Montana as Attaining/Unclassifiable for the 2010 SO2 standard, with the exception of the a portion of Yellowstone county which was previously designated as Attainment. As required in the SO2 DRR (40 CFR 51.1205), Montana DEQ is required to submit: an annual report of SO2 emissions at Talen Montana, LLC’s Colstrip Steam Electric Generating Station. This requirement is addressed within Appendix G to this Plan.

E. Lead (Pb) Monitoring Criteria On November 12, 2008, EPA lowered the NAAQS for Pb to 0.15 µg/m3 (micrograms per cubic meter) (73 FR, 66964). In addition, the rule established a design criteria for Pb in 40 CFR 58, Appendix D, Section 4.5 (a) requiring ambient air monitoring of certain sources which are expected to or have been shown to contribute to a maximum concentration in ambient air in excess of the Pb NAAQS. These regulations require, at a minimum, the installation of one source-oriented SLAMS site to measure the maximum Pb concentration in the ambient air resulting from each non-airport Pb source which emits 0.50 or more tons per year (tpy), and from each airport which emits 1.0 or more tpy. Currently, Talen Montana, LLC’s Colstrip Steam Electric Station located in Rosebud County and Montana Resources located in Silver bow County are the only sources which have reported Pb emissions in excess of 0.5 tpy. No airport in Montana has reported emissions in excess of the monitoring threshold.

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Talen Montana, LLC’s Colstrip Steam Electric Generating Station has historically reported total lead emissions in excess of 0.5 tpy. As stated in 40 CFR 58, Appendix D, Section 4.5 (a) (ii) the Regional EPA Administrator may waive the requirement stated above if the local air agency can demonstrate the Pb source will not contribute to a maximum Pb concentration in ambient air in excess of 50% of the NAAQS (based on historical monitoring data, modeling, or other means). On May 18, 2018, the State of Montana submitted a monitoring waiver request and along with supporting documentation to EPA Region 8 to forego monitoring in Colstrip due to modeled Pb concentrations in the ambient air less than 50% of the NAAQS. EPA Region 8 granted a waiver from the Pb monitoring requirement in Colstrip on November 5, 2018. Montana Resources operates an open pit copper and molybdenum mine, and associated processing facilities, located in Butte, Montana. The source-oriented Pb monitoring requirement was triggered by Montana Resources through reported 2017 estimated Pb emissions of 1.86 tons; as presented in the 2017 National Emission Inventory (initially released in August of 2019). The DEQ, as well as other entities, have monitored for Pb as well as other parameters from various locations with the Butte community since the early 1960’s. Based on consistent confirmation of the Butte-Greeley (30-093-0005) station as the highest point of concentration, from historic and near-term monitoring data results, the DEQ has consolidated monitoring resources overtime to the single Butte-Greeley site. No exceedance of the Pb NAAQS has been observed in the Butte area; including from the Butte-Greely site. DEQ acknowledges the obligation to address the recently triggered requirement of 40 CFR 58, Appendix D, Section 4.5 (a); and as such, is presently evaluating options to address this obligation.

F. Particulate Matter (PM10) Monitoring Criteria The minimum number of PM10 monitoring sites required by 40 CFR 58 Appendix D Section 4.6 is shown in Table 11.

Table 11 - Minimum PM10 Monitoring Requirements(1)

Number of Monitors per MSA(1)

Population category High concentration(2) Medium concentration(3) Low concentration(4)(5)

>1,000,000 6–10 4–8 2–4

500,000–1,000,000 4–8 2–4 1–2

250,000–500,000 3–4 1–2 0–1

100,000–250,000 1–2 0–1 0

(1) From Table D-4 of Appendix D to 40 CFR Part 58 -- Selection of urban areas and actual numbers of stations per MSA within the ranges shown in this table will be jointly determined by EPA and the DEQ

(2) High concentration areas are those for which data exceeds the PM10 NAAQS by 20 percent or more (3) Medium concentration areas are those for which data exceeds 80 percent of the PM10 NAAQS (4) Low concentration areas are those for which data is less than 80 percent of the PM10 NAAQS (5) The low concentration requirements are the minimum which apply in the absence of a design value

No MSAs in Montana currently meet the combination of population and PM10 concentration listed in Table 11. However, the DEQ continues to operate a network of PM10 monitors throughout the state serving various objectives. DEQ operates PM10 monitors in seven areas previously designated as nonattainment for the 24-hour PM10 NAAQS as required by EPA and to demonstrate the adequacy of PM10 control plans or maintenance plans for those areas which have received resdesignation to attainment. Those areas include Butte (30-093-0005), Columbia Falls (30-029-0049), Kalispell (30-029-0047), Libby (30-053-0018), Missoula (30-063-0024), Thompson Falls (30-089-0007), and Whitefish (30-029-0009).

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The DEQ also operates PM10 monitors in several areas in an attempt to further define background concentrations and spatial distribution of this pollutant within the state of Montana. These areas include Sidney (30-083-0002), Broadus (30-075-0001), Birney (30-087-0001), Malta (30-071-0010) and Lewistown (30-027-0006). Table 12 summarizes the 24-hour average values measured at PM10 monitoring sites operated by the DEQ during 2019. PM10 monitoring is discussed further in Section II.

Table 12 – 24-Hour Average Monitored PM10 Values for 2019(1)

Concentration (μg/m3) NAAQS Design Values (2)

Site Min Max Average 2019 2017 - 2019

Birney(3) 1 53 10.1 -- --

Broadus(3) 0 116 15.9 -- --

Butte 3 69 20.0 0 0

Flathead Valley 0 49 11.2 0 0

Kalispell 8 96 23.3 0 0

Lewistown 0 34 7.5 0 0

Libby 4 65 16.3 0 0

Malta 0 27 7.2 0 0

Missoula 2 85 16.6 0 0

Sidney - 201 0 59 9.7 0 0

Thompson Falls 1 43 12.1 0 0

Whitefish 3 86 18.1 0 0 (1) Dataset excludes DEQ defined exceptional events (2) PM10 Design Values are in the form of numbers of estimated exceedances as calculated by the

USEPA Air Quality System database in accordance with the procedure in 40 CFR 50 Appendix K (3) Designated as Special Purpose Monitor (SPM) which are non-regulatory (NAAQS excluded) as they

do not meet appropriate sighting criteria for the spatial scale of representation (See Section I of this Plan)

G. Fine Particulate Matter (PM2.5) Monitoring Criteria The minimum number of PM2.5 monitoring sites required by 40 CFR 58 Appendix D Section 4.7 is shown in Table 13.

Table 13 – Minimum PM2.5 Monitoring Requirements(1)

Number of Monitors per MSA

MSA population(2)

Most recent 3-year design value ≥85% of any PM2.5NAAQS(3)

Most recent 3-year design value <85% of any PM2.5NAAQS(3)(4)

>1,000,000 3 2

500,000 - 1,000,000 2 1

50,000 - <500,000 1 0 (1) From Table D-5 of Appendix D to 40 CFR Part 58. Minimum monitoring requirements applicable to MSA

(2) Population based on latest available census figures (3) PM2.5 NAAQS levels and forms are defined in 40 CFR part 50 (4) Minimum monitoring requirements apply in the absence of a design value

As described in Appendix B of this Plan, Montana possesses three MSAs (Billings, Missoula, and Great Falls), and all three fall into the smallest population category listed in Table 13. Missoula is the only Montana MSA that has at any time demonstrated a PM2.5 design value greater than 85 percent of the NAAQS, though it has not done so for nearly a decade. Consequently, no PM2.5

monitors or near-road PM2.5 monitors are required within Missoula or any community in Montana based on the current criteria.

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Because PM2.5 is a pollutant of concern within Montana, the DEQ’s PM2.5 monitoring network goes well beyond the minimum requirements as specified in Table 13. DEQ, along with several county air quality programs, operate PM2.5 monitors in various locations to demonstrate continuing NAAQS compliance, to provide information to various health departments PM2.5 control strategies, and to inform the public of potential health impacts during both winter inversions and summer wildfire events.

DEQ continues to operate a PM2.5 monitor in the community of Libby as required by EPA and to demonstrate the adequacy of the PM2.5 maintenance plan resulting from the resedisgnation from nonattainment to attainment for the 24-hour PM2.5 NAAQS. In addition, DEQ operates PM2.5 monitors in Sidney (30-083-0002), Broadus (30-075-0001), Birney (30-087-0001), Malta (30-071-0010) and Lewistown (30-027-0006) in an attempt to further define background concentrations and spatial distribution of this pollutant within the state of Montana. Additionally, DEQ operates multipurpose community-based monitors in Billings (30-111-0087), Bozeman (30-031-0019), Butte (30-093-0005), Columbia Falls (30-029-0049), Dillon (30-001-003), Frenchtown (30-063-0037), Great Falls (30-013-0001), Hamilton (30-081-0007), Helena (30-049-0026), Missoula (30-063-0024), and Seeley (30-063-0038). These sites, along with the NCore site (30-049-0004) located north of Helena, meet the requirements of 40 CFR Appendix D Section 4.7.3 to install and operate at least one regional background and at least one regional transport PM2.5 monitoring site within the network. Table 14 summarizes the 24-hour average values measured at the PM2.5 monitoring sites operated by the DEQ during 2019.

Table 14 – 24-Hour Average Monitored PM2.5 Values for 2019(1)

NAAQS Design Values (μg/m3)

Concentration (μg/m3) 2019 2017 - 2019

Site Min Max Average 98th Pctl. 24 hour Annual

Billings – Lockwood 0.9 19.0 5.70 10.4 14 6.6

Birney 0 19.0 4.07 11.0 11 4.7

Bozeman(2) 0 31.1 6.77 -- -- --

Broadus 0 27.0 5.13 12.3 16 5.9

Butte 0 30.0 5.18 19.7 23 6.4

Dillon(2)(3) 0 15.0 2.38 -- -- --

Flathead Valley 0 36.4 6.44 24.0 22 6.9

Frenchtown 1.4 57.9 8.33 24.4 22 8.2

Great Falls(2) 0 16.3 5.4 -- -- --

Hamilton 0 23.2 4.61 18.4 24 6.2

Helena-Rossiter 0 47.0 8.38 29.4 34 8.2

Lewistown 0 11.9 3.59 8.5 10 3.9

Libby 1.4 33.4 11.42 29.1 28 11.1

Malta 0 11.2 3.92 9.6 10 4.3

Missoula 0 26.2 6.99 18.6 21 7.1

Ncore 0 16.0 2.25 9.1 10 2.7

Seeley(2) 0 48.0 10.67 -- -- --

Sidney - 201 0 16.3 4.44 10.8 11 4.7

Thompson Falls(2) 0 32.5 6.78 -- -- -- (1) Dataset excludes DEQ defined exceptional events (2) Monitors are non-Federal Equivalent Method (non-FEM) monitors operated for informational purpose only and are not

certified to produce NAAQS-comparison data (3) Data is not currently reported to AQS

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The PM2.5 monitoring criteria in 40 CFR 58, Appendix D, contains two additional significant requirements. First, Section 40 CFR 58, Appendix D, Section 4.7.2 requires that states operate continuous analyzers in at least one-half of the required PM2.5 monitoring sites (per Table 13, above). The continuous monitors must be designated as Federal Equivalent Method (FEM) analyzers, and at least one analyzer per MSA must be collocated with an episodic Federal Reference Method (FRM) analyzer. As previously discussed, no PM2.5 monitors are required by federal Monitoring Network Design Criteria rule to be operated in any Montana community, so the CFR Section 4.7.2 criteria does not currently have direct application in Montana. However, PM2.5 is a significant pollutant in Montana, and impacts from summer wildfires and wintertime inversions have established a strong demand for continuous, near-real time PM2.5 data for assessing public health impacts as well as determining NAAQS compliance. To meet this need DEQ’s PM2.5 network is comprised solely of continuous monitors; with FRM monitors used only for collocation, validation, and quality assurance (QA) purposes. As a result, the national discussion regarding the accuracy and representativeness of continuous monitors is of great significance to DEQ and to the citizens of Montana. Second, 40 CFR, Appendix D, Section 4.7.4 requires that each state continue to conduct PM2.5

Chemical Speciation monitoring at locations designated to be part of the national Speciation Trends Network (STN) that are operated as part of the Chemical Speciation Network (CSN). Two sites in Montana are currently included in the CSN; Butte (30-093-0005) and NCore (30-049-0004). Appendix E contains a list of the chemical components for which analysis is performed on filters collected at these stations.

H. National Core Monitoring Site (NCore) Monitoring Criteria Section 3 of Appendix D to 40 CFR 58 requires that each state operate at least one NCore multipollutant monitoring site. By definition, each NCore site must include monitoring equipment to measure PM2.5, PM10-2.5, speciated PM2.5, O3, SO2, CO, NO, NOY, and meteorology. The majority of NCore sites across the nation are established in urban areas. In Montana however, the NCore site was established as a long-term trend background site in an area believed to be relatively pristine and un-impacted by anthropogenic sources. The Montana NCore site (Sieben’s Flat, 30-049-0004) was installed in late 2010. All parameters are functional and acquiring ongoing data. The monitoring directives in 40 CFR Appendix D Section 4.8.1 contains specific requirements for the operation of monitors for PM10-2.5 at NCore sites. These requirements are currently limited in application to NCore monitoring sites and are fully met in Montana’s NCore site at Sieben’s Flat.

I. General Monitoring Network Design Considerations

1. Monitors Not Meeting Siting Criteria

The DEQ designs its network and operates the air monitoring sites in compliance with EPA’s requirements for ambient air monitoring sites (40 CFR Part 58, Appendices A, C, D and E). Within the DEQ’s network there are three sites that do not meet all of the siting requirements of 40 CFR Part 58, Appendix E. The Hamilton (30-081-0007) PM2.5 site is located within 15 meters of paved city streets, but is operated as a neighborhood-scale site and not intended as a “traffic corridor” monitor as discussed 40 CFR 58 Appendix E

12

Section 6.3. The roads receive low traffic counts, and EPA has approved (granted a waiver) of the continued operation of this site as a neighborhood scale site in response to previous Annual Network Report documents submitted by the DEQ.

Two PM10 monitors located in eastern Montana, Broadus (30-075-0001) and Birney (3-087-0001), were established to define background concentrations of this pollutant on a neighborhood or broader scale. Each of these sites is located in a remote region, and of logistic necessity, near unpaved gravel roads traveled by ranching and agricultural equipment. As a result, the monitors are unduly influenced by that traffic and are not appropriately representing background PM10 concentrations in their intended scaled scope. However, DEQ desires to continue to operate these monitors as part of a suite of instruments located at these sites. Consequently, in its 2012 Network Plan the DEQ proposed to designate the PM10 monitors at Broadus and Birney as special purpose monitors producing non-regulatory (SPM-NR), or NAAQS excluded, data. EPA approved this designation on April 8, 2013.

2. PM2.5 Spatial Scales and Monitoring Methods

The data from PM2.5 monitoring sites with spatial scales designated as smaller than “neighborhood” is generally not used for PM2.5 NAAQS compliance review purposes in the DEQ’s network. Currently, the only PM2.5 site in the Montana network of this nature is the Overlook Park station in Great Falls (30-013-0001). All PM2.5 monitors designated as Federal Reference Method or equivalent (FRM/FEM) generate data suitable for determining compliance with the PM2.5 NAAQS. However, DEQ has historically operated non-FEM PM2.5 monitoring equipment for general information purposes, and will continue to do so. The tables in Appendix C discriminate between FRM, FEM and non-FEM PM2.5 instrumentation operated within the DEQ’s network.

3. Quality Assurance Project Plan (QAPP)

Federal rules and associated guidance establish a significant grid of quality assurance requirements, and the DEQ operates its monitoring network within these requirements. Of note is the requirement in 40 CFR 58 Appendix A, Section 2 for each monitoring organization to develop and describe its quality system within a written QAPP. The DEQ’s QAPP underwent an update which was adopted by the Montana Board of Environmental Review on February 9, 2018.

13

II. Changes to the Monitoring Network

A. Introduction DEQ regards the requirement to develop and submit an Annual Network Plan as an opportunity to review the existing air monitoring network and to plan for future needs. In the process of producing this document, DEQ reviews air pollutant trends, known and projected emission changes, and revisions to the NAAQS and monitoring rules; then attempts to balance those realities against available resources. Likewise, in 2015 the DEQ completed a periodic network assessment in accordance to 40 CFR 58.10(d). The changes proposed in this document reflect the results of both efforts. Immediate changes are proposed in this annual network plan, while long-term evaluation and direction of DEQ’s air quality surveillance system continue to be addressed within the periodic network assessment, and the resulting system modifications. DEQ anticipates occasional changes to the focus and direction of Montana’s air monitoring network in response to future federal rulemaking. No network changes completed since submission of the 2019 Annual Monitoring Network Plan and no changes to Montana DEQ’s air monitoring network are proposed for the 2020 planning period.

B. Ongoing Network Changes

1. PM10 Monitoring in Nonattainment Areas

As indicated in previous network plans, diminishing monitoring resources necessitate a redirection of monitoring efforts toward those pollutants and geographic areas that have the greatest potential human health impacts or are of the greatest national concern. As a result, we would like to reiterate our belief that historical PM10 monitoring from multiple sites has served its purpose and needs to be discontinued so that the resources associated with those efforts can be redirected to areas and pollutants of a higher priority. In light of this, DEQ continues to work on resdesignation of nonattainment areas for PM10. The Missoula nonattaminment area was redesignated to attainment effective on June 24, 2019. The Kalispell, Columbia Falls, and Libby nonattainment area resdesignations were approved by USEPA on March 20, 2020, the comment period has closed and are awaiting final action. The Butte nonattainment area redesignaion request and demonstration package was submitted to USEPA for review on March 30, 2020. DEQ will seek to address the remaining PM10 nonattainment resignations in the next planning period.

2. Fine Particulate Monitoring (PM2.5)

As previously discussed, PM2.5 is a pollutant of concern within Montana. DEQ is continuously look for opurtinities to expand Montana’s PM2.5 monitoring network using a assortment of air quality instruments which balances the need for regulatory quality NAAQS comparable data, as well as the necessity to provide quality data to the public and local health departments for general use. To this end DEQ is expoloring the possible integration of lower-cost air quality sensors into the fine particulate network. A variety of sensor instrumentation are in the field under test conditions in order to gauge operation and data acquisition functionality, and to provide a comparison to current regulatory methods. DEQ will look to employ this sensor technology during the next several years.

14

DEQ will continue to rely on high-accuracy regulatory methods to monitor fine particulate air quality impacts, as well as its existing cache of portable monitors for use during high-impact events (i.e. wildfires) or special studies.

14

III. Appendices

15

Appendix A

Monitoring Site Locations

16

Montana Department of Environmental Quality

Ambient Air Monitoring Site Location Summary

AQS No. City - Site Name Montana Address Longitude Latitude CBSA

30-111-0066 Billings Coburn Road Coburn Hill Rd. -108.458780 45.786579 Metro Billings, 13740

30-111-0087 Billings-Lockwood 2320 Old Hardin Road -108.426551 45.806357 Metro Billings, 13740

30-087-0001 Birney Tongue River SR 566, 3 Miles N of Birney -106.489820 45.366151 -- --

30-031-0019 Bozeman High School N 15th Avenue, H.S. Parking Lot -111.056282 45.683765 Micro Bozeman, Gallatin County, 14580

30-075-0001 Broadus Powder River Big Powder River Road East -105.370283 45.440295 -- --

30-093-0005 Butte Greeley School Alley Btwn N. Park Pl. and S. Park Pl. -112.501247 46.002602 Micro Butte, Silver Bow County, 15580

30-001-0003 Dillon State Hwy 91 S. and Barrett St. -112.642516 45.206442 -- --

30-029-0049 Flathead Valley 610 13th St West -114.189272 48.363694 Micro Flathead County, 28060

30-063-0037 Frenchtown Beckwith 16134 Beckwith Street -114.224273 47.012907 Metro Missoula, Missoula County, 33540

30-013-0001 Great Falls Overlook Park 10th Ave. S. and 2nd St. E. -111.303317 47.494318 Metro Great Falls, Cascade County, 24500

30-081-0007 Hamilton PS#46 Madison and 3rd St. S. -114.158889 46.243621 -- --

30-049-0026 Helena Rossiter Pump House 1497 Sierra Rd. East -112.013089 46.658762 Micro Helena, 25740

30-029-0047 Kalispell Flathead Electric E Center St. and Woodland Ave. -114.305334 48.200540 Micro Kalispell Area, Flathead County, 28060

30-027-0006 Lewistown 303 East Aztec Drive -109.455315 47.048537 -- --

30-053-0018 Libby Courthouse Annex 418 Mineral Ave. -115.552280 48.391672 -- --

30-071-0010 Malta 2309 Short Oil Road -107.862471 48.317507 -- --

30-063-0024 Missoula Boyd Park 3100 Washburn Rd. -114.020549 46.842297 Metro Missoula, Missoula County, 33540

30-063-0038 Seeley Lake Elem. School School Lane -113.476182 47.175630 Metro Missoula, Missoula County, 33540

30-083-0002 Sidney 201 Intersection of Hwy 201 and Cnty R 326 -104.676864 47.867900 -- --

30-049-0004 Sieben’s Flat NCore I-15 Exit 209, then Sperry Dr. -111.987164 46.850500 Micro Helena, 25740

30-089-0007 Thompson Falls High School Golf and Haley -115.323746 47.594395 -- --

30-029-0009 Whitefish Dead End End of 10th St. -114.335973 48.400523 Micro Flathead County, 28060

17

Montana Ambient Air Quality Monitoring Sites

18

Appendix B

Montana Core Based Statistical Areas (CBSAs)

19

CBSA definition per 40 CFR 58.1: “Core-based statistical area (CBSA) is defined by the U.S.

Office of Management and Budget, as a statistical geographic entity consisting of the county or counties associated with at least one urbanized area/urban cluster of at least 10,000 population, plus adjacent counties having a high degree of social and economic integration. Metropolitan Statistical Areas and Micropolitan Statistical Areas (MSAs) are the two categories of CBSA (metropolitan areas have populations greater than 50,000; and Micropolitan areas have populations between 10,000 and 50,000). In the case of very large cities where two or more CBSAS are combined, these larger areas are referred to as combined statistical areas (CSAs).

Montana Core Based Statistical Areas(1)(2)

CBSA Code CBSA Title

Metropolitan or Micropolitan

Statistical Area

Estimated Total

Population County/County Equivalent

Estimated County

Population

FIPS State Code

FIPS County Code

Central or Outlying County

13740 Billings, MT Metro 172,846

Golden Valley County 821 30 037 Outlying

Carbon County 10,725 30 009 Outlying

Yellowstone County 161,300 30 111 Central

33540 Missoula, MT Metro 119,600 Missoula County 119,600 30 063 Central

24500 Great Falls, MT Metro 81,366 Cascade County 81,366 30 013 Central

14580 Bozeman, MT Micro 114,434 Gallatin County 114,434 30 031 Central

28060 Kalispell, MT Micro 103,806 Flathead County 103,806 30 029 Central

25740 Helena, MT Micro 81,653 Jefferson County 12,221 30 043 Outlying

Lewis and Clark County 69,432 30 049 Central

15580 Butte-Silver Bow, MT Micro 34,915 Silver Bow County 34,915 30 093 Central

(1) U.S. Census Bureau, Population Division; Office of Management and Budget, Metropolitan and Micropolitan Statistical Areas. (2) US Census Bureau Population Estimate as of July 1, 2019.

20

Montana Metropolitan Statistical Areas (MSAs)

Montana Micropolitan Statistical Areas

21

Appendix C

Monitoring Network Summary

22

Ambient Air Quality Monitoring Network By Location With Proposed or Actual Changes

AQS Number Site Name Pollutant Parameter -

POC

Method

Frequency

Spatial Scale

Monitoring Objective(4)

2020 Change Code Note(1) PM(2) Type(3)

30-111-0066 Billings-Coburn SO2 42401-1 600 7 Continuous SLAMS Neigh. H,S none

SO2 - 5 min 42406-1 600 7 Continuous SLAMS Neigh. H,S none

30-111-0087 Billings-Lockwood PM2.5 88101-3 170 8 FEM Continuous SPM Neigh. P none

30-087-0001 Birney

NO 42601-1 574 11 Continuous SLAMS Regional B none

NO2 42602-1 574 11 Continuous SLAMS Regional B none

NOX 42603-1 574 11 Continuous SLAMS Regional B none

O3 44201-1 047 9 Continuous SLAMS Regional B none

PM10 81102-1 150 15 FEM Continuous SPM NR Neigh. B none

PM2.5 88101-3 183 16 FEM Continuous SLAMS Regional B none

30-031-0019 Bozeman PM2.5 88502-3 731 5 Non Continuous SPM NR Neigh. P none

30-075-0001 Broadus

NO 42601-1 574 11 Continuous SLAMS Regional B none NO2 42602-1 574 11 Continuous SLAMS Regional B none NOX 42603-1 574 11 Continuous SLAMS Regional B none O3 44201-1 047 9 Continuous SLAMS Regional B none

PM10 81102-1 150 15 FEM Continuous SPM NR Neigh. B none

PM2.5 88101-3 183 16 FEM Continuous SLAMS Regional B none

30-093-0005 Butte-Greeley

PM10 81102-4 122 4 FEM Continuous SLAMS Neigh. H,P none

PM2.5 88101-3 170 8 FEM Continuous SLAMS Neigh. H,P none

PM2.5 88101-2 116 2 FRM 1 in 6 SLAMS QA Coll(5) none

PM2.5 Spc'n Various 6 1 in 6 SLAMS(7) Neigh. H,P none

30-001-0003 Dillon PM2.5 88502-1 734 17 Non Continuous SPM NR Neigh. P none

30-029-0049 Flathead Valley PM10 81102-1 122 4 FEM Continuous SLAMS Neigh P none

PM2.5 88101-3 170 8 FEM Continuous SLAMS Neigh P none

30-063-0037 Frenchtown PM2.5 88101-3 170 8 FEM Continuous SLAMS Neigh. P none

30-013-0001 Great Falls-OP PM2.5 88502-3 731 5 Non Continuous SPM NR Middle H,P none

30-081-0007 Hamilton PM2.5 88101-3 170 8 FEM Continuous SLAMS Neigh. H,P none

30-049-0026 Helena-Rossiter

PM2.5 88101-3 183 16 FEM Continuous SLAMS Neigh. H,P none

PM2.5 88101-2 116 2 FRM 1 in 6 coll(5) SLAMS QA Coll(5) none

PM2.5 88101-4 170 8 FEM Continuous SPM QA Coll(6) none

30-029-0047 Kalispell-FEC PM10 81102-1 122 4 FEM Continuous SLAMS Neigh. H,P none

30-053-0018 Libby PM10 81102-1 150 15 FEM Continuous SLAMS Neigh. H,P none

PM2.5 88101-3 183 16 FEM Continuous SLAMS Neigh. H,P none

30-027-0006 Lewistown

NO 42601-1 599 10 Continuous SPM Regional B none

NO2 42602-1 599 10 Continuous SPM Regional B none

NOX 42603-1 599 10 Continuous SPM Regional B none

O3 44201-1 047 9 Continuous SPM Regional B none

PM10 81102-1 150 15 FEM Continuous SPM NR Neigh. B none

PM2.5 88101-3 183 15 FEM Continuous SPM Regional B none

30-071-0010 Malta

NO 42601-1 599 10 Continuous SPM Regional B none

NO2 42602-1 599 10 Continuous SPM Regional B none

NOX 42603-1 599 10 Continuous SPM Regional B none

O3 44201-1 047 9 Continuous SPM Regional B none

PM10 81102-1 150 15 FEM Continuous SPM NR Neigh. B none

PM2.5 88101-3 183 16 FEM Continuous SPM Regional B none

30-063-0024 Missoula-Boyd

O3 44201-1 047 9 Continuous SLAMS Neigh. P none

PM10 81102-6 122 4 FEM Continuous SLAMS Neigh. H,P none

PM2.5 88101-3 170 8 FEM Continuous SLAMS Neigh. H,P none

30-049-0004 NCore-Sieben Flats

CO 42101-1 554 13 Continuous NCore Region B none

NO 42601-1 674 14 Continuous NCore Region B none

NOy 42600-1 674 14 Continuous NCore Region B none

O3 44201-1 047 9 Continuous NCore Region B none

SO2 42401-1 600 14 Continuous NCore Region B none

PM2.5 88101-3 170 8 FEM Continuous NCore Region B none

PM2.5 88101-1 116 2 FRM 1 in 3 NCore Region B none

PM2.5 Spc'n Various 6 1 in 3 SLAMS(7) Region B none

PMcoarse 86101-1 185 12 FEM Continuous SLAMS Region B none

Continued...

23

Ambient Air Quality Monitoring Network By Location With Proposed or Actual Changes (continued)

AQS Number Site Name Pollutant Parameter -

POC

Method

Frequency Type(3) Spatial Scale

Monitoring Objective(4)

2020 Change Code Note(1) PM(2)

30-063-0038 Seeley Lake PM2.5 88502-3 731 5 Non Continuous SPM NR Neigh. H,P none

30-083-0002 Sidney 201

NO 42601-1 599 10 Continuous SLAMS Neigh. S none

NO2 42602-1 599 10 Continuous SLAMS Neigh. S none

NOX 42603-1 599 10 Continuous SLAMS Neigh. S none

O3 44201-1 047 9 Continuous SLAMS Neigh. S none

SO2 42401-1 600 7 Continuous SLAMS Neigh. S none

SO2 - 5 min 42406-1 600 7 Continuous SLAMS Neigh. S none

PM10 81102-1 150 15 FEM Continuous SLAMS Neigh. S none

PM2.5 88101-3 183 16 FEM Continuous SLAMS Neigh. S none

30-089-0007 Thompson Falls PM10 81102-3 122 4 FEM Continuous SLAMS Neigh. H, P none

PM2.5 88502-3 731 5 FEM Continuous SPM NR Neigh. P none

30-029-0009 Whitefish PM10 81102-1 122 4 FEM Continuous SLAMS Neigh. P none (1) Method Notes

1 Teledyne-API Model 300 Nondispersive infrared CO analyzer (FEM)

2 BGI-PQ200 with very sharp cut cyclone (FEM)

4 MetOne BAM 1020 Beta Attenuation Monitor (PM10 FEM)

5 MetOne BAM 1020 Beta Attenuation Monitor with PM2.5 sharp cut cyclone (SCC)

6 MetOne / URG Speciation Air Sampling System

7 Teledyne‐API Model T100U Ultraviolet SO2 fluorescence (FEM)

8 MetOne FEM‐BAM 1020 with PM2.5 very sharp cut cyclone Beta attenuation monitor (PM2.5 FEM)

9 Thermo Model 49i UV Photometric O3 analyzer (FEM)

10 Teledyne‐API Model T200U Chemiluminescence analyzer NO/NOx/NO2 (FRM)

11 Thermo Model 42i TL Chemiluminescence NO/NOx/NO2 analyzer (FRM)

12 MetOne BAM1020 PM10‐2.5 measurement system -- Paired beta attenuation monitors (FEM)

13 Thermo Model 48i-TLE enhanced trace level CO analyzer

14 Thermo Model 42i-TLE. NO-DIF-NOy chemiluminescent specialty trace level gas analyzer

15 Thermo Scientific 5014i Beta Attenuation Monitor for PM10 (FEM)

16 Thermo Scientific, 5014i Beta Attenuation Monitor for PM2.5 (FEM)

17 MetOne E-BAM Beta Attenuation Monitor with PM2.5 sharp cut cyclone (SCC)

(2) Method PM Monitor Type: FEM = Federal Equivalent Method, FRM = Federal Reference Method, Non = Not FEM or FRM method (3) Monitor Site Type:

SLAMS : State or Local Air Monitoring Station

SPM : Special Purpose Monitor

QA Col: Quality Assurance, Co-located Monitor

ID : Industrial Monitor

NR : Non-Regulatory Data

CSN : Chemical Speciation Network (4) Monitoring Objective Descriptions: B = Background, H = Highest Concentration, P = Population Exposure, S = Source Impact (5) "Coll" = collocated sampler (6) "Continuous - Coll" = collocated continuous (BAM) sampler (7) Network Affiliation: CSN-STN

Summary of Proposed or Actual Changes to the Existing Ambient Air Quality Monitoring Network

AQS Number Site Name Pollutant Description of Change(s) Network Plan

Reference

No changes proposed

24

Appendix D

Ambient Air Quality Raw Data Summary, Calendar Year 2019

25

Site Parameter Units

Annual Values(1) Data Capture

NAAQS Comparison(2) NAAQS(3)

Min. Max. Ave. # > # > 85% Short-Term Extended

Billings - Coburn Road SO2 ppb 0 26.5 0.7 97 0 0 75 500

Billings Lockwood PM2.5 ug/m3 0.9 66.7 6.0 80 1 1 35 12

Birney - Tongue River NO2 ppb 0 11 0 98 0 0 100 53

OZONE ppm 0.001 0.065 0.029 96 0 25 0.070 --

PM10 STD ug/m3 0 91 11.2 98 0 0 150 --

PM2.5 ug/m3 0.2 19.0 4.30 95 0 0 35 12

Bozeman High School PM2.5 ug/m3 0.9 31.1 6.8 93 0 1 35 12

Broadus - Powder River NO2 ppb 0 14 0 67 0 0 100 53

OZONE ppm 0.005 0.16 0.033 97 3 30 0.070 --

PM10 STD ug/m3 1 116 16.7 96 0 0 150 --

PM2.5 ug/m3 0 27.0 5.33 97 0 0 35 12

Butte - Greeley School

PM10 STD ug/m3 3 69 20.1 99 0 0 35 12

PM2.5 ug/m3 0 30.0 5.28 98 0 1 35 12

Dillon PM2.5 ug/m3 0 15.0 2.38 98 0 0 35 12

Flathead Valley (Columbia Falls HS)

PM10 STD ug/m3 0 49 11.6 98 0 0 150 --

PM2.5 ug/m3 0 36.4 6.66 98 1 2 35 12

Frenchtown - Beckwith PM2.5 ug/m3 1.4 57.9 8.48 99 1 1 35 12

Great Falls - Overlook Park PM2.5 ug/m3 1.1 37.5 5.61 99 1 1 35 12

Hamilton - PS #46 PM2.5 ug/m3 0 23.2 4.61 99 0 0 35 12

Helena - Rossiter Pump House

PM2.5 ug/m3 0.2 53.0 8.62 99 2 8 35 12

PM2.5 COL ug/m3 0.2 44.3 6.29 98 2 2 35 12

Kalispell - Flathead Electric PM10 STD ug/m3 8 96 23.6 99 0 0 150 --

Lewistown - Lewistown NO2 ppb 0 14 0 98 0 0 100 53

OZONE ppm 0.005 0.065 0.035 95 0 30 0.070 --

PM10 STD ug/m3 0 41 7.8 98 0 0 150 --

PM2.5 ug/m3 0 27.8 3.8 98 0 0 35 12

Libby - Courthouse Annex PM10 STD ug/m3 4 65 16.6 100 0 0 150 --

PM2.5 ug/m3 1.4 36.1 11.61 97 1 7 35 12

Malta - Malta NO2 ppb 0 15 0 97 0 0 100 53

OZONE ppm 0.003 0.071 0.031 99 1 13 0.070 --

PM10 STD ug/m3 0 33 7.5 99 0 0 150 --

PM2.5 ug/m3 0 19.0 4.05 100 0 0 35 12

Missoula - Boyd Park OZONE ppm -- -- -- -- -- -- 0.070 --

PM10 STD ug/m3 2 85 17.0 98 0 0 150 --

PM2.5 ug/m3 0.7 26.2 7.19 98 0 0 35 12

NCore - Sieben's Flat CO TRACE ppb 7 728 128 84 0 0 35000 9000

NOY ppb 0 9.7 1.2 85 -- -- -- --

OZONE ppm 0 0.07 0.035 98 4 67 0.070 --

PM10 STD ug/m3 0 61 7.1 96 0 0 150 --

PM2.5 ug/m3 0 20.9 2.30 90 0 0 35 12

PMCOARSE ug/m3 0 17 3.9 87 -- -- -- --

SO2 ppb 0 18.4 0.3 93 0 0 75 0.5

Seeley - Elementary School PM2.5 ug/m3 0.1 48.0 10.8 99 3 8 35 12

Sidney - 201 NO2 ppb 0 15 1 96 0 0 100 53

OZONE ppm 0.073 0.033 95 4 44 0.07 0.070 --

PM10 STD ug/m3 0 69 9.8 95 0 0 150 --

PM2.5 ug/m3 0 16.8 4.50 98 0 0 35 12

SO2 ppb 0 14.4 0.4 95 0 0 75 500

Thompson Falls High School PM10 STD ug/m3 1 43 12.2 95 0 0 150 --

PM2.5 ug/m3 0.8 32.5 6.82 98 0 1 35 12

Whitefish - Dead End PM10 STD ug/m3 3 86 18.4 99 0 0 150 -- (1) Based on 1-hour average values for gaseous parameters and 24-hour average for particulate. Dataset does not exclude DEQ defined flagged exceptional events. (2) Short-Term NAAQS standard comparison only. Comparison based on 8-hour rolling average for ozone, 1-hour average values for all other gaseous pollutants, and 24-hour average values

for particulates. Comparisons are based on highest values observed and does not account for the calculated form of the standard (See Appendix G for actual NAAQS standard). Count of values above the given NAAQS are for reference only and does not necessarily indicate an exceedance of a standard occurred.

(3) NAAQS averaging times (for reference only):

Averaging Time CO NO2 Ozone PM2.5 PM10 SO2

Short-term 1-hour 1-hour -- 24-hour 24-hour 1-hour

Extended 8-hour Annual 8-hour Annual -- 3-hour

26

Appendix E

PM2.5 Speciation Analytes

27

28

29

Appendix F

National and Montana Ambient Air Quality Standards

30

FEDERAL & STATE AIR QUALITY STANDARDS

Pollutant Averaging Period Federal (NAAQS) State (MAAQS) NAAQS Standard Type

Carbon Monoxide (CO) 1-Hour 35 ppm a 23 ppm b Primary

8-Hour 9 ppm a 9 ppm b Primary

Fluoride in Forage Monthly NA 50 µg/g c NA

Grazing Season NA 35 µg/g c NA

Hydrogen Sulfide (H2S) 1-Hour NA 0.05 ppm b NA

Lead (Pb) Quarterly 1.5 µg/m3 c, o 1.5 µg/m3 c NA

Rolling 3-Month 0.15 µg/m3 c NA Primary & Secondary

Nitrogen Dioxide (NO2) 1-Hour 100 ppb d 0.30 ppm b Primary

Annual 53 ppb e 0.05 ppm f Primary & Secondary

Ozone (O3) 1-Hour NA g 0.10 ppm b Primary & Secondary

8-Hour 0.070 ppm h NA Primary & Secondary

Particulate Matter ≤ 10 μm (PM10) 24-Hour 150 µg/m3 j 150 µg/m3j Primary & Secondary

Annual NA 50 µg/m3 k Primary & Secondary

Particulate Matter ≤ 2.5 μm (PM2.5)

24-Hour 35 µg/m3 l NA Primary & Secondary

Annual 12.0 µg/m3 m NA Primary

Annual 15.0 µg/m3 m NA Secondary

Settleable PM 30-Day NA 10 g/m2 c NA

Sulfur Dioxide (SO2)

1-Hour 75 ppb n 0.50 ppm p Primary

3-Hour 0.5 ppm a NA Secondary

24-Hour 0.14 ppm a, q 0.10 ppm b Primary

Annual 0.030 ppm e,q 0.02 ppm f Primary

Visibility Annual NA 3 x 10-5/m f NA a Federal violation when exceeded more than once per calendar year. b State violation when exceeded more than once over any 12-consecutive months. c Not to be exceeded (ever) for the averaging time period as described in either state or federal regulation. Pb is a 3-year assessment period for attainment. d Federal violation when 3-year average of the 98th percentile of the daily maximum 1-hr average at each monitoring site exceeds the standard. e Federal violation when the annual arithmetic mean concentration for a calendar year exceeds the standard. f State violation when the arithmetic average over any four consecutive quarters exceeds the standard. g Applies only to NA areas designated before the 8-hour standard was approved in July, 1997. MT has none. h Federal violation when 3-year average of the annual 4th-highest daily max. 8-hour concentration exceeds standard. i To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone concentrations measured at each monitor within an area over each

year must not exceed 0.08 ppm. (3) Final rule signed October 1, 2015, and effective December 28, 2015. The previous (2008) O3 standards additionally remain in effect in some areas. Revocation of the previous (2008) O3 standards and transitioning to the current (2015) standards will be addressed in the implementation rule for the current standards.

j State and federal violation when more than one expected exceedance per calendar year, averaged over 3-years. k State violation when the 3-year average of the arithmetic means over a calendar year at each monitoring site exceed the standard. l Federal violation when 3-year average of the 98th percentile 24-hour concentrations at each monitoring site exceed the standard. m Federal violation when 3-year average of the annual mean at each monitoring site exceeds the standard. n Federal violation when 3-year average of the 99th percentile of the daily maximum 1-hr average at each monitoring site exceeds the standard. Final rule June 22, 2010. o The 1978 Pb NAAQS will remain effective until one year after designations are effective for the October 15, 2008, revised Pb NAAQS (0.15 µg/m3), except in existing

Pb nonattainment areas (East Helena, MT). In East Helena, EPA will retain the 1978 Pb NAAQS until EPA approves attainment and/or maintenance demonstrations for the revised Pb NAAQS.

p State violation when exceeded more than eighteen times in any 12 consecutive months. q The 1971 SO2 NAAQS will remain effective until one year after designations are effective for the June 2, 2010, revised SO2 NAAQS (75 ppb), except in existing SO2

nonattainment areas (Laurel and East Helena, MT). In Laurel and East Helena, EPA will retain the 1971 SO2 NAAQS until EPA approves attainment and/or maintenance demonstrations for the revised SO2 NAAQS.

31

Appendix G

Annual SO2 Data Requirements Rule Report

32

On August 10, 2015, EPA finalized the Data Requirements Rule (DRR) for the 2010 1-hour SO2

primary NAAQS (40 CFR 51, Subpart BB). The SO2 DRR required that air agencies identify and

characterize air quality around large sources. Talen Montana, LLC’s Colstrip Steam Electric

Generating Station, a coal-fired power plant located in Rosebud County, was the sole source in

Montana identified as applicable to the rule. As required in the rule for characterizing air quality for

the primary 2010 SO2 NAAQS, Montana DEQ submitted the appropriate designation of attainment

for Rosebud County to the EPA as demonstrated through modeling on December 20, 2016. On

January 9, 2018, EPA classified Rosebud County as Attainment/Unclassifiable (40 CFR Part 81).

As required in the SO2 DRR (40 CFR 51.1205), Montana DEQ is required to submit: an annual report

of SO2 emissions at Talen Montana, LLC’s Colstrip Steam Electric Generating Station; an assessment

of the cause of any emission increases compared with modeled emissions; and a recommendation

regarding if additional modeling is needed to ensure compliance with the rule. The following

information is intended to meet those requirements.

1. Summary of Emissions

Table 1 shows a summary of the three years of actual emissions modeled for the DRR compared to

2019 actual emissions as provided by Talen Montana, LLC for each of its coal-fired.

Table 1. Emission Summary at Colstrip Steam Electric Generating Station

Modeled Emission Sources

Modeled Actual SO2 Emissions (tons/year) 2019 Actual SO2

Emissions (tons/year)

Emission Change Compared to Modeled

Average 2012 2013 2014 Average

(2012-2014)

Unit 1 2,212.03 4,109.70 2,467.51 2,929.74 1668.42 -43%

Unit 2 2,589.72 4,889.66 3,393.30 3,624.23 2117.08 -42%

Unit 3 2,144.72 2,533.16 2,057.54 2,245.14 2324.18 4%

Unit 4 2,257.88 942.34 2,303.83 1,834.68 2215.19 21%

Colstrip Total

9,204.35 12,474.86 10,222.18 10,633.79 8,324.87 -22%

2. Assessment of the Cause of Emission Increases

Annual SO2 emissions in 2019 were lower for Unit’s 1 and 2 compared to the average annual

emissions used for modeling. Unit 3’s 2019 emissions slightly higher than the actual 2012 and 2014

emissions. In 2019, Unit 4 emissions were higher than the actual 2013 emissions because the unit was

shut down for an extended period in 2013, as noted in the modeling demonstration. Overall,

emissions from Colstrip are 22 percent lower in 2019 compared to the 3-year average annual modeled

emissions.

3. Recommendation Regarding Additional Modeling

Total emissions are 22 percent less than the modeled emissions; therefore, no further modeling is

recommended to show compliance with the 1-hour SO2 NAAQS.

33

Appendix H

Public Inspection & Comment

34

The 2020 Ambient Monitoring Network Plan was made available for public inspection and comment as required by 40 CFR 58.10(a)(1) on June 1, 2020. A single response to public inspection and comment was received on June 30, 2020, by Bison Engineering (Bison), on behave of Montana Resources. The response specifically addressed Plan elements under Section E - Lead Monitoring Criteria, pertaining to the recently triggered requirement under 40 CFR 58, Appendix D, Section 4.5 (a) which mandates ambient air monitoring for sources emitting 0.50 tpy or greater of lead. Montana Resources operates an open pit copper and molybdenum mine, and associated processing facilities, located in Butte, Montana. The source-oriented Pb monitoring requirement was triggered by Montana Resources through reported 2017 estimated Pb emissions of 1.86 tons. Bison’s comment package presented a discussion of the current and ongoing ambient Pb monitoring activities Montana Resources engaged Bison to conduct at the Greeley School in Butte, as well as an analysis and assessment of data collected to date through this monitoring project, along with perspectives offered by historic data collected by various entities. Ultimately comments points to a conclusion that sufficient scientific evidence exists to support a demonstration that Montana Resourcces will not contribute to a maximum Pb concentration in ambient air in excess of 50 percent of the NAAQS.

As established with Section E to this plan, DEQ is presently evaluating options to address this Pb monitoring obligation. DEQ will review the information and ascertions submitted by Bison and will incorporate into the formal plan as appropriate. The comments were revieced via electronic mail and are included within Appedix I to this Plan.

35

Appendix I

Public Comment Recieved